In some fields it is useful to image the phase distribution in polycrystalline samples with small crystals or crystallites of one or more materials.
One approach that has been used is to use X-ray fluorescence. Imaging detectors may be used to build up an image of X-ray fluorescence across a sample and hence image the location of particular elements or phases. However, this approach is not suitable in all cases and in particular X-ray fluorescence only distinguishes the elements not the specific crystal or crystal phase concerned.